The steering rod is connected to the output shaft of the electric motor by means of a screw-nut screw coupling, it is movable along the cited axis to control the steering of a pair of wheels of the vehicle, and has, normally, an external thread connected to an internal thread made on the output shaft of the electric motor.
Since the steering rod has the cited external thread and protrudes outside the cited frame, the steering units for known electric vehicles of the type described above show some drawbacks mainly arising from the fact that the correct operation of the screw-nut screw coupling can be compromised by dust, dirt, and/or by other polluting agents with which the external thread of the steering rod comes into contact.